Servo drive mechanisms for slides, conveyors and like systems have been known and some provide limited crash protection by having a drive that is sturdy or compliant enough to survive an abrupt stop caused by a crash or other abnormal conditions. These prior servo drive mechanisms require brakes, electrical switches and programmed homing sequences to shut the system down and to resynchronized it for further use. A variety of arrangements with motor transducers, motor brakes, load transducers, load brakes and single position detent clutches have been used to provide limited crash protection. The high cost and complexity of such devices make improvements desirable in the area of economy, simplicity and reliability.